Pyrolized coal tends to be activated and bond with oxygen. Accordingly, when the pyrolized coal is stored as it is, the coal may react with oxygen in the air and spontaneously combust due to heat generated by this reaction. In view of this, the pyrolized coal is exposed to a processing gas atmosphere containing a low concentration of oxygen to deactivate the coal by making it bond with oxygen in advance, and spontaneous combustion in storage is thus prevented.
When characteristics (for example, type of coal, particle diameter, amount of water content, stored period, and the like) of the aforementioned coal being the target of pyrolysis and conditions of the pyrolysis (for example, pyrolysis temperature, pyrolysis time, pyrolysis processing amount, and the like) of the coal vary, the degree of activity of the pyrolized coal supplied to deactivation processing also varies. Accordingly, when pyrolized coals with different degrees of activation are subjected to the deactivation processing by a deactivation processing device under the same condition, the degree of activity of the pyrolized coal (upgraded coal) subjected to the deactivation processing and discharged from the deactivation processing device varies.
When the pyrolized coal is excessively subjected to the deactivation processing, the amount of oxygen contained in the upgraded coal increases and the heating value of the upgraded coal decreases depending on the amount of contained oxygen. Meanwhile, when the deactivation of the pyrolized coal is insufficient, the upgraded coal may react with oxygen in the air and spontaneously combust due to the heat of this reaction while the upgrade coal is stored in, for example, a coal yard. Accordingly, in order to obtain an upgraded coal which has a sufficient heating value and which does not spontaneously combust in long-term storage and thus has good handling characteristics, the upgraded coal needs to be adjusted to an appropriate degree of inactivity.
For example, Patent Document 1 listed below describes a coal deactivation processing device as follows. The device takes part of upgraded coal produced by subjecting pyrolized coal to deactivation processing as a sample and puts the sample into an evaluation device main body. Then, oxygen-containing gas of a predetermined temperature is supplied into the evaluation device main body, and the temperature of the gas discharged from the evaluation device main body is measured. If a measured value exceeds a threshold value, the device determines that the degree of inactivity of the upgraded coal is insufficient, and adjusts the oxygen concentration of the processing gas in the deactivation processing of the pyrolized coal.
Patent Document 2 listed below describes a method of using blended coal which is prevented from spontaneously combusting by mixing active coal and inactive coal such that the blended coal has an oxygen adsorption rate equal to or lower than the oxygen adsorption rate of coal for which safety is confirmed.